Question: Which of these numbers is composite? ${5,\ 17,\ 19,\ 59,\ 63}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 5, 17, 19, and 59 each have only two factors. The factors of 63 are 1, 3, 7, 9, 21, and 63. Thus, 63 is the composite number.